The target animal possessed by an astirax does additional magic drain on its next successful attack to the target of the attack. The astirax is able to drain an additional 1d4 spell energy from the attack per three levels of the caster (to a maximum of +4d4 or a total drain pf 5d4). The addition is +1d4 at 5th level and increases to +2d4 at 10th level, to +3d4 at 15th level and to the maximum of +4d4 at 20th level. The spell lasts until the possessed animal makes a successful attack or the spell duration expires.